As is generally known, cobalt-base alloys have found utility in a number of diverse applications. Indeed, such alloys, particularly the alloy designated STELLITE 6 (nominally 1%C - 28%Cr - 5%W - balance Co), have dominated the general market for wear resistant high temperature overlay materials, since they do manifest excellent hot hardness and weldability properties. Such attributes notwithstanding, the recent spiraling prices for cobalt together with uncertainty of supply have intensified efforts in evolving alternative materials.
To be an acceptable replacement for cobalt-base hard facing compositions, an alloy should exhibit a high level of hardness at 800.degree. to 1200.degree. F. and good weldability. Moreover, hard facing materials should be amenable to a variety of deposition processes, including automatic processes of high production rates, e.g., plasma transferred-arc welding (PTAW). This too, has been a virtue of the cobalt-base materials.
There are nickel-base alloys commercially available but many of these contain substantial amounts, relatively speaking, of silicon and boron. And while they have found utility, the inherent inability to provide adequate wear resistance at elevated temperatures has detracted from their use in successfully competing with the cobalt alloys, particularly as trim for applications such as automotive valves.